Yup: I heard about it just today, in fact. An FCP user was trying to get Cinema Tools to conform 24fps footage from a Mk II and Mk III to 25. No problems with the Mk II footage, but no luck with the Mk III footage.

Now, it could be just coincidence. But if you don't believe in coincidence, you might think that there's something screwy with Canon's new codecs for the Mk III. "Screwy" is a highly technical term, by the way.

Okay found Quicktime 7.6.6 for SnowLeopard and installed it. Now I have Quicktime 7 in the utilities folder but importing *.mov files from the 5D Mark III still crashes After Effects and Premiere CS6. Moving Quicktime 10 to the trash bin didn't helped either.